In fact there is a bug in CSS (in)validator that I tried
to report some time ago but failed as www-validator-css discussion list
bounced all my messages.
The test suite is simple:
and {display:block}
which is completely valid CSS 1/2/2.1/3
but is not recognized by (in)validator as such,
here is what it says:
Errors
Line: 0
Parse error - Unrecognized : and {display:block}
Best wishes,
George